I'm no expert,all of my scopes have 1" tubes, but from what I have read on this and other forums the only real advantage that the 30mm scopes give you is more range of adjustment. So, if you can shoot to the yardage you want with a 1" tube it's good enough, at least until you want to shoot farther.
The 10FP that my Police Dept. issued me has a Leupold 3x9x40 tactical, Farrell base and rings. The elevation adjustment tops out at about 800 yards. A friend has the scope you are looking at, Zeiss Conquest, on a PSS 308, he can get about the same yardage. I just put together my own 10FP, money is a little tight right now with the wife sick so I went with a Sightron 4x16x42 MD and a 20MOA Farrell base hoping to get to 1000 yards. Haven't shot it yet. Point is, if you plan to shoot to 700 yards a 1" tube will normally do the job, if you want to shoot farther then go with a 30mm tube or a canted base. That Zeiss is a nice scope.